piers, the 54 m high temporary pylon, the cable stay
tensioning platforms and the inside and outside of the
arch. All of these cranes were required to supply the
materials for the casting of each segment as follows:
To build the first 21 segments of each semi-arch, two
tower cranes were needed. The height of the cranes
was approximately 135 m to avoid interferences with
the temporary steel towers. They were placed next to
the arch foundation and built on a micropiled
foundation. Due to their height, they were braced at
approximately half of their length to avoid buckling.
Once the 21 segments were finished, the cranes were
dismantled and moved to the next position over the
arch.
Cranes over the arch:
The same cranes, but with its height reduced to 85 m,
were assembled on the previously cast 20th segment
of each semi-arch. To achieve this, a docking structure
that allows the connection between the crane feet
and the segment inclined surface was designed.
Because of the height where the jib is placed, there
were no interferences with the temporary steel
towers, allowing complete rotation. Due to the
magnitude of the punching loads transmitted by the
crane feet, with compressions over 5 MN and
tractions over 4 MN, it was necessary to introduce
some modifications to the segments where the
cranes were placed to ensure a correct load
transmission.
Once the 38th segment was completed, cranes 3 and
4 were assembled over the arch. To avoid
interferences between jibs, these cranes were 45 and
35 m high. These cranes have no cabin and anchored
at 50 m over the arch foundation. The adaptation of
the segment to receive the loads from the cranes was
also necessary, as well as that of the docking
structure between the crane feet and the segment
surface.
The cranes’ operations were possible because of a
platform designed to exchange materials placed on
the 31th and 32th segments. The outer cranes placed
the materials on the platform and the inner cranes
took these materials to the form traveler system.
The concrete feeding was undertaken by two
concrete skips with a volume of 2 m3, so that while
the inner crane was pouring one in the formwork, the
outer one was refilling the other.
Aerodynamic effects have again been studied to
check the behavior of the cranes and the arch under
adverse wind conditions.
Fig. 3: Schematic of the cranes needed in the arch construction.
4/2016